In this paper, we investigate a super dense cellular deployment case in which the cells are continuously added in order to increase the total network capacity. The effect of the other cell interference in the HSPA network is analyzed, which provides an insight into the aggregated interference impact on the cell capacity. The network capacity performance with varying cell densities has been studied with system-level simulations. The results show that there is an upper bound existing for the total HSDPA downlink capacity when continuously adding cells within an open area. This paper can serve as essential guidelines both for macro cell densification and small cell deployment. It is recommended that careful considerations need to be taken if an operator intends to improve network performance by adding cells to their networks in dense urban cities.